Hydraulic brake



June 19, 1945. M. sHuMAN HYDRAULIC BRAKE Filed Maron 20, 1944 I N VEN TOR.' M. SAL/MAN 'gradually undergo l n make up for wearing down ofthe brakelmmg, 10

` modications are embodied,

Patented June 19, 1945 UNITEDVi STATES PATENTl OFFICE r- V 2,s'1s,662-v y j yH5zpI't'AyUrLIolinnnE I Moses ShumangWest llos Angeles, Calif. 'i .s Application Maranza, 1944, serial No, 527,214

' ,y 11jo1aims. (otrasvasi Thisinvention relates to brakes such as used onl the wheels of motor vehicles and has lpar-ticus lar reference to means ior'automatically adjustingsuch brakes toy variations in operating conditions due to wear of the-brake lining, heat expansion of 'the brake drum and other commonly known causes.

Such devices as have come to my notice will automatic vreadjustment to andY may in such cases prove satisfactory;`t But Y the samevdevices will also'instantly respond to brake drum expansion, due to overheating, the f moment the brake pedal-is depressed to-set the brake, and they will vremain so set.v When ysubsequently the brake drum cools off and shrinks, 1t is found that this overadjlristedy mechanism locks thelbrake. y f

It is the general object of my invention to provide a simple and inexpensivev attachment to the 20 conventional type of brakemechanism and which is capable of such automaticself-adjustment. More particularly, it is the object tofprovide a mechanism which, under ordinary working: conditions will function-in the conventional manner g2g;

but which, 'under abnormal conditions of'wear or excessive expansion duev toheat 'generation will automatically undergo the vreadj'ustment necessary in order to assure proper functioningr of the brake. It is the further obje'ctof the invention Q0 to provide [means which, l when :the -mechanism hasfhthus automatically becomeoveradjusted, will limmediatelyv restore the mechanismv ytognormal l 'functioning upon subsequent operation -ofv the brake. ii Witnuiese anal other*objeeiainyievi/,tne inrvention consists in the combinationshereinafter fully described, lparticularlypointedout linthe appended claims, andy illustrated. in the `accompanying drawing, of which;

' Fig; v1 is aside elevational view .of a conventional hydraulic brakemechanism to which the deviceof theV invention is'shown attached; y

,A Fig. 2 illustrates, ona larger scale, the upper portion of the device of Fig. l; and ,4 Fig. f3 shows, ona still largerscal'e, one of the parts' .ofvthe device in which certain adjustment .The brake mechanism shown'fin the drawing is' siibsiantijaiiy as foi-ind yiny various vwen" known 5ol automobiles, comprising a4 rotatable brakel drum I, withinwhich,is'journaled ap'air of brake shoes f1', 3 onarstationary supportIa, as "usual-in prac-l 'y tice. ,'The. upper ends o'fy the conventional shoes I contact pistons 4, `5y of a iiuid'pressure cylinderfy` ,in the conventional shoe, -but modied by the introduction of a pawl .I 0, which is pivotallymounted. on each shoe at II. The lower end of this pawl is shaped to engage the teeth I2a of a lever I2, which is'shown pivotally hungon a studs9` of the stationary support and a spring I 3 urges this -pawl against a stop -I4 to maintain it in -this po- ,sition,V vAs in the conventional brakemechanism, 15 the pressure Ifluid which is introduced into the cylinder 6 upon depression of the brake pedal forces the shoes apart until the brake lining I5 contacts the inner periphery of the brake drum andcontinues to exercise increasing pressure until sufficient pressure is developedto overcomethe vtension tof the spring I3, whereuponl the pawl is caused to turn on vits pivot, ysubstantially into the Iposition shown in dotted outline in Fig. 2, there- V, urged against the pointed end of the pawl IIJ, and

itis made with a slot I1, in which a stud I6 rides. This slot affords substantially the same extent of movement vto the lever .in the direction of advance' movement of the brake shoe that-is usually given tothe latter, 'and it is by-a spring I8 causedto follow this advance movement of the ypawland shoe, f Upon release of the brake pedal,

itfis found that the pawl instantly enters the notch from which it previously was raised, and

. that the spring 1',whiohlis much more powerful than the spring I8, returns the parts to theii` initial positions. It is rimportant to note that the slot r-I-I is merelymlong. enough to) aord the lever ,IZjthis normal operating movement. f

Where thebrake is properly adjusted, and before the movement of the brake shoes is inf creased due to wear of the brake lining, the pawl 5 will return each time to ,the notch from which it rose,-, butas the lining vwears thinner and the brake `shoe movement correspondingly increases, and also because themovement of thelever I2 is limited to the normal brake shoe movement, ,it vis found that the pawl Amay be returned to the next notch I2 following notch I2b before the brake shoe pressure isfully relieved. In this manner, Yit is seen that the brake mechanism readjusts itself `to compensate for wear of the brake lining, and this readjusting operation may continue until If the stud I6 were rigidly mounted in position e on the stationary support, it is seen that .it would be impossible to free the braker when so locked. However, it is important to note :that athis istud is mounted on a second lever 20, which also is pivotally hung on the stud l9; A lstud 2`| 'or the stationary support is shown seated in a slot 22 of` the lever 20, and this slot is long enough to afford the lever movement for release :of the locked brake, -as lwill now be described.

.A spring 23 maintains thelever'ZU iin the normal position *indicated lin Fig. v2, -and -it is timportant to `notethat this spring -is `powerful enough to overcome the Ltensionofloothsprings?! and |28. For this reason, it is 4found that the spring will maintain the lever 'Z0 vin the `normalposition under all lordinary operating conditions, as iii the `stud has been part of vthe stationary support. But, when it is remembered that the 'spring '|93 swings the pawl rIl) into engagement with fthe teeth o'f the lever |2 them'oment pressure "on the brake pedal is released, it is seen that the vrgreat Ypressure exerted by `the cooling and 'contracting 1i 'drum flange against the brake shoe and thepawl |"0 is more `thansuiiicient toovercome the tension of the 'spring -23 and so to swing the "lever 2U on its pivot vto release thebrake. Upon Lsubsequent operation `of the brake, after the drum flange has fully contracted, 'it is 'found that all `the parts will return vto the normal position fo'f 2.l

"Because a brake mechanism such las fhere shown isset 'to-'operate within very close limits,

it is relatively expensive tomanuiactura 'Itiisjii course, that this adjusting means, Iwhere required,

should *be applied to "both levers 12. '1t `is alsoto be noted that the same adjusting ffeaturemay'be added to 'the llevers 20', "ifffound necessary'.

'The drawing is merely illustrative y'of the invention. The'parts have fbeenlundulyf-spread out,

their shapes `modiriedand sizesexaggerated,` 'all in order lto simplify `reading of fthe drawing I do, for this reason, 4not Wish to belimited'tothe exact shapes, proportions or arrangements of partsA shown, but reserve the vriglrit to embody such modiiications ias will iall'vvithin the Ascope of the claims hereto appended. Noris it "myintention to -limit 'the device of my invention to use-onmolris' yno .tor vehicles, .but yit may be .employed Wherever ,such mechanism is-.adaptable.

silient means for maintaining said yshoes re-,

prising two axially separable pistons, a pawl on each shoe maintained in contact with said pistons by said resilient means, mechanism on the support associated With said pawls capable of automatic overadjustment corresponding to abnormal increase in brake shoe movement, and means for `automatically returning said mechanism to position of normal adjustment upon Isubsequent restoration of normal brake shoe movement. e

2. naihydraulic brake, va rotating brake drum, a stationary support, brake shoes on said support, :resilient means for maintaining said shoes retracted, hydraulic shoe advancing means com- `prising two axially separable pistons, a pawl on :each shoe :maintained in contact with said pistons by said resilient means, mechanism associated with "said Apavvls capable of automatic readjustment `to compensate for increased brake shoe movement due to Wear of shoe lining and capable @of :overadjustment corresponding .to abnormal 'brake shoe ,movement-due Ito heat :expansion of the brake drum, and means for automatically re- -turningfsaid .mechanism to -positionofnormal adjustment :in ,response to A'subsequent .restoration of normal :brake shoe movement Lupon cooling and contraction of the brake drum.

3. In ahydraulicfbrake, a rotating brake drum, .a stationarysupport,fbrake shoes on said support, resilient .'fmeans for :maintaining said shoes reftractedhydraulic shoe advancing means comprising two axially `separable pistons, a pawl on veach shoemaintained in contact with said pistons by said resilient means, Lmechanism associated with-said Lpawls ,capable ofrnaintaining the .pawls Eand lthe .shoes in 1any position 4of overadjustment fduring 'periods :of :excessive heat expansion .of .the brake drum, said mechanism being capableof .automat-ica'lly returning tto position `of 4normal adjustment lof fthe shoes iin response ito subsequent restoration .of normal-shoe movement upon coollingA and shrinking of the ybrake-drum.

4. '1n a hydraulic brake, Ia rotating .brake drum, va .stationary support, brake shoes on .said .sup-

llport, resilient zmea-ns gior :maintaining said shoes lretracted, lhydraulic shoe :advancing means ,com- -prising :two faxially .separable pistons, a pawl on each .shoe maintained in contact ,with said pisftons lby .said resilient means, La member lon said support :positioned for engagement by each pawl automatically 'to :maintain -each vshoe in correct retracted iposition, 'to :advance :each `shoe in order to-compensateorwearrof the lining thereof and to any position fof overadjustment Aduring periods of heat expansion of the brake drum, said member being capablefof 'automatic `readjustment to Areturn fthe 4'pawl and 'brake shoe vto position of 4normal adjustment upon Vsubsequent cooling and shrinking of the drum;

5. In a hydraulic brake, a rotatingbrake drum, `a stationary support, brake shoes on said support, resilient means for `maintaining said shoes .retractedh-ydraulic shoe advancing means comprising two axiallyseparable pistons, `a pawl on `each shoe tmaintained in .contact with said pistons -by said resilient means, a mechanism on the support normally engaged .by v.each pawl .auto- `matically Ito maintain eachshoe `in ,-normal reitracted 'ipositionand in :any position `-of overad- 'justment f during .periods .of Aheat expansionof the drum, A:said member 'being ycapable of automatic readjustment to return Lthe pawl .and shoe to position `of `normal ,adjustment upon -subsequent cooling land shrinking of the drum, and means for adjusting said mechanism to correct any error yin normalretracted position of the parts.

said support, resilient means maintaining said' shoes retracted, shoe spreading means including two axially separable pistons, brake adjusting 'means on said support for limited movement in the direction of the brake shoe movement, a pawl on each shoe heldvby said resilient means in contact with said pistons and having a portion thereof positioned for engagement with said adjusting means to limit return movement of the shoes,

means impelled by contraction of the brake drum due to cooling thereof following overheating expansion to increase the return movement of the shoes.

'7. In a brake mechanism, in combination with a brake drum, a stationary supportwithin said drum, a brake shoe on sai-d support, resilient means retracting said shoe from the drum, and shoe advancing means including a piston, brake adjusting means` comprising, a lever mounted` for limited oscillation on said support and having a toothed end surface, and a pawl on the brake shoe abutting said piston and having a -pollton positioned for engagement with the teeth of said surface to limit return movement of the shoe.

8. In a brake mechanism, the combination with a brake drum, a. stationary support within said drum, a brake shoe on said support, resilient means Aretracting said shoe from the drum and shoe advancing means including a piston, of brake adjusting means comprising, a lever 4mounted for limited oscillation on said support i movement of the shoe, and means urging said pawl into engagement with saidrteeth.

9. In a brake mechanism, the combination with a brake drum, a stationary support within said drum, a brake shoe on said support, resilient abutting said piston and made with a portion shaped to engage the teeth of said. surface to return the lever against the tension of said spring thereby to limit the return movement of the shoe.

10. In a brake mechanism, the combination with a brake drum, a stationary support, a brake shoe on said support, resilient means retracting said shoe from the drum, and shoe advancing means including a piston, of brake adjusting means comprising, a lever mounted on a pivot of j the support for limited oscillation thereon and and means associatedr with said brake, adjusting I having a toothed end surface, a spring urging said lever forward, a second lever hung on the same pivot and mounted for limited oscillation relative to said first named lever,'a pawl on the shoe abutting said piston and made with a portion adapted to engage the teeth of said surface to return the first named lever against the tenvsion of its spring, and a spring urging said secmeans retracting said shoe from the drum and shoe advancing means including a piston, vof brake adjusting means comprising, a lever mounted for limited oscillation on said support and having a toothed end surface, a spring urging the lever forward, and a pawl on the shoe ond lever forward, said last named spring being powerful enough to resist the pressure of the returning brake shoe pawl and first lever but incapable of resisting the additional pressure exerted during brake drum contractions following expansion due to overheating.

411. In a brake mechanism, the combination with a brake drum, a stationary support, a brake vshoe on said support, resilient means retracting said shoe from the drum', and shoe advancing means including a piston, of brake adjusting means comprising, a lever mounted on a pivot of the support for limited oscillation thereon and having a toothed end surface, a spring urging said lever forward, a second lever hung on the same -pivot and mounted for limited oscillation relative to said first named lever, means for adjusting the position of one lever relative to the other, apawl on lthe shoe abutting said pistonv and` made with a portion shapedito engage the teeth of saidv surface to return the first lever against the tension of its spring, and a spring urging said second lever forward, the last named spring being powerful enough to resist the pressure of the returning shoe the pawl and the first lever butincapable of resisting the ad-ditional 'pressure exerted by the shoe and pawl during brake drum contractions following expansion due to overheating and incidental overadjustment of the brake adjusting means.

MOSES SHUMAN. 

